In 1944 Knutson described a formula for estimating age specific DMFT means from the percent of individuals in the age group having one or more decayed, missing or filled teeth. This formula, together with two other formulas are evaluated simultaneously for different age ranges, and for different allowable maximum percentages. Results indicate that appropriate restrictions of age range, and maximum percent of individuals with one or more DMF teeth, are far more important than choosing the "right" formula. The formula: X equals AY over G-Y with A equals 3.117 and G equals 179, where X is the estimated DMFT mean, and Y is the percent of individuals with one or more DMF teeth is, however, considered preferable to the other formulas based on ease of computation.